Abstract Purpose To examine tracking of weekday and weekend screen time (ST; i.e., television TV and computer PC time) from early adolescence to early adulthood and to identify social ecological predictors of weekday and weekend ST among boys and girls separately. Methods Data were retrieved from elementary schools (n = 59) in Flanders (Belgium). At baseline, 1,957 children (age, 9.9 ± .43 years) and one of the parents filled out a questionnaire on sedentary behavior and individual, social, and environmental variables. After a 10-year follow-up period, six hundred fifty-five 20-year-olds (age, 19.9 ± .43 years) filled out an adapted questionnaire on sedentary behavior, of which 593 contained full data at baseline and follow-up. Multiple regressions were performed to examine predictors (baseline) of ST (follow-up), and logistic regressions were used to analyze tracking of ST. Results For boys, a consistent positive predictor of weekday and weekend TV and PC time at follow-up was ST at baseline ( p < .01). For girls, drinking more soda at baseline predicted more weekday and weekend TV and PC time at follow-up ( p ≤ .02). Some other individual variables also predicted ST in both boys and girls. Tracking was only found among boys; those exceeding the ST guideline at baseline were three to five times more likely to exceed this guideline at follow-up ( p  ≤ .001). Tracking was not present among girls. Conclusions To minimize TV and PC time during early adulthood, interventions for adolescent boys should focus on minimizing ST. For girls, focus should be on healthy eating. However, more research is warranted to confirm these conclusions.